Neonatal recent thymic emigrants (RTE): phenotypic and functional comparison to adult RTE (85.16)

Abstract

Abstract Neonatal CD4+ T cells typically produce high levels of IL-4, resulting in Th2-biased responses. The neonatal CD4+ compartment contains a high frequency of recent thymic emigrants (RTE), in contrast to the small proportion found in adults. Using intrathymic labeling to identify RTE, it has been described that adult RTE produce high levels of IL-4. Thus, neonatal Th2 biased responses may result from their over-represented RTE population. Here we have compared neonatal and adult CD4+ RTE for the first time, using a mouse strain that allows for the identification and purification of RTE from the periphery. In contrast to the intrathymic labeling system, adult RTE from these mice produced less IL-4 and IFNγ than the resident cells. Similarly, neonatal RTE produced less of both IL-4 and IFNγ than resident neonatal cells. The phenotypic changes accompanying post-thymic maturation of RTE were also similar in neonates and adults. Thus, both neonatal and adult RTE appear to require a period of post-thymic maturation to acquire mature Th2 and Th1 function and phenotype. Importantly, despite these similarities, neonatal RTE produced more IL-4 than adult RTE. Together, these results indicate that neonatal and adult RTE differ functionally but the subsequent processes of post-thymic maturation are similar in early development and adult life. This work was supported by NIAID grant number R01 AI44923-02 (B.A.)